Using ExodusII API version 4.98 and DB version 4.98 to export "…/filename.e".WARNING: The model contains 290526 nodes (and their attached elements) that will not be written to the genesis file. This may indicate a problem in element block assignments.

That usually means you have missed assigning some part of the mesh to a block. Check to see that all elements have a block assignment. You can draw individual blocks by picking their block ID from the tree view. If you only want to export a portion of the mesh, that message may be OK.